Magnetic amplifier controlled power circuit operative with d.c. electric source



March 1968 YOSHINORI KAWAI ETAL 3,374,440

MAGNETIC AMPLIFIER CONTROLLED PGWER CIRCUIT OPERATIVE WITH D. C ELECTRICSOURCE Filed NOV. 25, 1963 5 Sheets-Sheet 1 IN VEA/ 1219s HzsM AfsuK/WAK/ H/easm 5am ATTORNEY March 1968 YOSHINORI KAWAI ETAL 3,374,440

MAGNETIC AMPLIFIER CONTROLLED POWER CIRCUIT OPERATIVE WITH D.C. ELECTRICSOURCE Filed NOV. 25, 1963 5 Shets-Sheet 2 Fig. a

M f NIAWW NL2 62 7- D2 2 k3 SW v R f SCRz SCR/ 6/ EEO INVE/VTUIQSyasl-lllvael KA u Al HIS AKNS WAK/ 3, 22. A ORNEY March 19, 1968 FiledNov. I 25, 1965 Load few MAGNETIC AMPLIFIER CONTROLLED POWER CIRCUITOPERATIVE WITH D.C. ELECTRIC SOURCE YOSHINORI KAWAI ETAL 3,374,440

5 Sheets-Sheet 3 E 700 E g 600 b 8 \l /00 0 K50 2820 Job Confro/ currenfmA) fnla sAlwk YQSH/NOB/ KAWA/ ATTORNEY March 1968 YOSHINORI KAWAI ETAL3,374,440

MAGNETIC AMPLIFIER CONTROLLED POWER CIRCUIT OPERATIVE WITH D.C. ELECTRICSOURCE Filed Nov. 25, 1965 5 Sheets-Sheet 4 [NYE/V7012; YOSHINORI (Aw/A1ATTORNEY March 19, 1968 YOSHINORI KAWAI ETAL 3,37 ,4 0

MAGNETIC AMPLIFIER CONTROLLED POWER CIRCUIT OPERATIVE WITH D.C. ELECTRICSOURCE Filed Nov. 25, 1963 5 Sheets-Sheet 5 IL Load cums-m Confro/currem (mil H/ROS/l/ $470 ATTORNEY United States Patent ()fitice3,374,440 MAGNETEC AMPLIFIER CONTROLLED POWER CIRCUIT OPERATIVE WITH DC.ELECTRIC SOURCE Yoshinori Kawai, Katsuta-shi, Hisakatsu Kiwaki, Mitoshi,and Hiroshi Sato, Katsuta-shi, Japan, assignors to Hitachi, Ltd, Tokyo,Japan, a corporation of Japan Filed Nov. 25, 1963, Ser. No. 325,827Claims priority, application Japan, Nov. 24, 1962, 37/52,932 10 Claims.(Cl. 330-8) ABSTRACT OF THE DISCLOSURE A magnetic amplifier controlledpower circuit operable from a DC. source for feeding a load withproportionally controlled current. The power circuit is comprised by apair of saturable magnetic cores having a control winding wound on andextending over the pair of cores and a pair of output windings eachrespectively wound on one of the pair of cores. A pair of semiconductorswitching elements are provided each having two load electrodes and acontrol electrode, respectively. The load electrodes of each of thesemiconductor switching elements are connected in series with respectiveoutput windings, and a direct current electrical source and a load areconnected in common with each of the series connected semiconductorswitching elements and its series connected output winding. Turn oncircuits are connected to the control electrodes of each of theswitching semiconductor devices and to respective ones of the saturablecores for turning on the semiconductor switching elements in response tothe saturation condition of the cores. As a consequence of thisarrangement, the semiconductor switching elements are renderedconductive and non-conductive alternately in accordance with thesaturation and nonsaturation of the pair of magnetizable cores. Thecircuit is completed by means for applying a variable magnitude directcurrent control signal to the control winding to control the frequencyof turn-on and turn-off of the circuit to thereby proportionally controlthe pulsating power output from the amplifier.

This invention relates to magnetic amplifiers comprising a pair ofsaturable iron cores, and a pair of semiconductor switching elements,and operative with DC. electrical sources.

Most of theknown magnetic amplifiers comprise control windings, outputwindings, feedback windings, etc., respectively wound on saturable ironcores, with A.C. electric sources applied to the output windings throughrectifiers and loads, output currents being under control of controlcurrents.

It is an object of the present invention to provide magnetic amplifiersoperative with DC. electric sources.

Another object of the invention is to utilize control rectifiers forproviding large-capacity D,C.-operative magnetic amplifiers,

Another object of the invention is to provide largecapacity switchingelements having jumping characteristics by application of positivefeedback.

A further object of the invention is to provide magnetic amplifiersrelatively insensible to mechanical vibrations, with high fidelity, thusmaking themselves suitable for mounting on cars and aircrafts.

A further object of the invention is to provide an A.C.-energizedmagnetic amplifier with D.C.-auxiliary energy source which may beoperatively used when the A.C. source would have failed.

The present invention will best be understood from the followingdetailed descriptions of preferred embodiments 3,374,443 Patented Mar.19, 1968 of the invention with reference to the accompanying drawings;in which FIG. 1 is a circuit diagram showing an embodiment of theinvention;

FIGS. 2, 3 and 4 are curve diagrams to be utilized for explanation ofoperation of the magnetic amplifier shown in FIG. 1;

FIG. 5 is a circuit diagram showing another embodiment of the invention;

FIG. 6 is. a curve diagram to be utilized for explanation of operationof the device shown in FIG. 5; and

FIGS. 7 and 8 are circuit diagrams, respectively show ing furtherembodiments of the invention.

Referring now to FIG. 1 of the drawings, the magnetic amplifier showncomprises a pair of control rectifiers SCRI and SCR2, which may be knownthyratrons or silicon controlled rectifiers, diodes D1, D1 and D2, D2,saturable iron cores m1 and m2, and control windings NC, output windingsNLI, NL"1 and NLZ, NL2, and gate windings NG]; and NGZ, respectivelywound on the cores m1 and H22.

A DC. electrical source E0 is applied to output windings NL1, N112 andNL2, NL'l, through a load RL and a pair of silicon controlled rectifiersSCRl, SCR2, respec tively, gate windings N61 and N62 being connectedfrom the cathodes of respective silicon controlled rectifiers SCRI andSCRZ, through condenser C1, diode D1 and condenser CZ, diode D2. to thecontrol gates of SCRl and SCRZ, respectively. Condenser charging diodesD1 and D2 are connected between one end of each of the gate windings N61and N32 and the outer end of each of the capacitors C1 and C2,respectively. The magnetic amplifier shown further comprisescondensor-charging diodes D1 and D2, a commutating condensor C, and aDC. control or input voltage source Ec.

The operation of the device shown in FIG. 1 will now be described. It ishere assumed that SCRI is conductive, while SCR2 is non-conductive. E0is applied to windings NLI and NLZ through SCR1, and at the same time tothe circuit SCRi-CNL2NL'1. Condenser C is selected to be fully chargedwithin fairly a short period of time, so that the circuit ESCR1C-NL2NL'1RL-SWEO may be considered open substantially during theconducting period of silicon controlled rectifier SCRI.

By application of E voltage across windings NL'l and NLZ in series,voltages are induced in respective windings NGI and NG2 in thedirections shown by arrows in FIG. 1. Consequently, condenser C1 ischarged by the nowclosed circuit CIDl-.%SCR 1 (gate and cathode), whilecondenser C2 is charged through diode D2, in the polarities shownrespectively in FIG. 1. By this, the gate current of SCRl flows easily,while the gate current of SCR2 cannot flow by reason of the reverse biasof forward voltage-drop component of diode D2. This reverse bias servesto prevent SCRZ from its false operation with more or less noise.

The fluxes of cores m1 and m2 change gradually from saturation in onedirection to saturation in the other, respectively. Thus, when core m2has become saturated, the induced in gate winding NGZ becomessubstantially zero instantaneously, resulting in discharge of condenserC2 through D2 and gate-cathode of SCR2, which renders SCR2 conductive.

Consequently, the charge on condenser C is instantaneously dischargedthrough SCRl and SCRZ, the forwarddirection current decreasing below itsholding-current value, so that SCRl is rendered non-conductive. Thecommutating operation of SCRl and SCR2 is thus repeated indefinitelyalong with changes in states of cores m1 and m2 from one-directionsaturation to the other.

It is to be understood that transistors may be used inNL1=NL2:NLd=NL'2=NL (number of turns), the charging currents of C1, C2,etc.

are negligible, and the load current, control current and controlvoltage are assumed iL, I'C, and Ec, respectively:

where Q=charge on condenser C. =fiuX in core m1. =fiux in core m2.

Neglecting the magnetizing currents of cores m1 and 1112, these coresbeing not saturated,

where i =current flowing through NLi and NLZ. i =current flowing throughNLZ and NL'i. i =current flowing through the control circuit R -E N Fromthe above equations are obtained the following ones:

As a result, if E 20, qfi and 9 reach saturation simultaneously, but ifE 0, p reaches saturation before From Equations 1 and 2,

Thus, the change in is similar to that in Q.

Consequently, the voltage V across windings NLl and NL'2 in series isFIG. 2 shows waveforms of V and i, the horizontal dot line showing theaverage value of i, wherein i is the current flowing through RL.

If E becomes larger and larger, the period of time required for to reachsaturation becomes shorter and shorter, and the values become as shownin FIG. 3.

The characteristic curve of load current and control current at such atime is shown in FIG. 4. The present invention utilizes such astraight-line characteristic for providing magnetic amplifiers operativewith DC. electrical source, that is, the control curent mA (see FIG- URE4) is in the range of about zero to one hundred or minus one hundred.

According to the invention, each iron core may also be provided with afeedback winding N as shown in FIG. 5. By this, the load current is fedback positively, so that there may be obtained jumping characteristics(i), (2) or hysteresis characteristics (3), as shown in FIG. 6.

In order to start the device of present invention, a switch S may beprovided, as shown in FIG. 7, for shortcircuiting SCR-l, or condenserCl, resister R, etc., may be connected in parallel with SCRL Althoughnot illustrated, for starting, the DC. source E may be ditieruztiatedthrough a condenser and applied to the gate of SCRI.

FIG. 8 shows another embodiment of the invention, simplified by use oftransistors and having jumping characteristics.

What we claim is:

1. A magnetic amplifier controlled power circuit for feeding a load,comprising a pair of saturable magnetic cores, a control winding woundon and extending over both of said pair of cores, a pair of outputwindings each respectively wound on at least one of said pair of cores,a pair of semiconductor switching elements each having two loadelectrodes and a control electrode, respectively, with the loadelectrodes of each of said semiconductor switching elements beingconnected in series circuit relationship with at least one of saidoutput windings, a direct current electrical source and a load connectedin series circuit relationship in common with each of the seriesconnected semiconductor switching elements and its series connectedoutput Winding, turn on circuit means coupled between the controlelectrodes of said switching semiconductor devices and at least one loadterminal of the semiconductor switching elements and responsive to thesaturation condition of the saturable magnetic cores for turning on thesemiconductor switching elemen'.s in response to the saturationcondition of the cores whereby the semiconductor switching elements arerendered conductive and non-conductive alternately in accordance withsaturation and non-saturation of said pair of magnetizable cores, andmeans for applying a variable magnitude direct current control signal tothe control winding for variably controlling the rate of saturation ofthe saturable magnetic core.

2. A magnetic amplifier controlled power circuit according to claim I,in which said semiconductor switch elements are transistors.

3. A magnetic amplifier controlled power circuit according to claim 2 inwhich the turn-on means opcratively coupled to the control electrodes ofthe switching semiconductor devices and respective ones of the saturablecores is comprised by a limiting impedance connected between the baseelectrode of each of the transistors and the juncture of the loadterminal of the opposite transistor with its series connected outputwinding.

4. A magnetic amplifier controlled power circuit according to claim 1wherein the turn-on means comprises respective gate windings wound oneach of said saturable Cores and circuit means operatively coupling saidgate windings to the control electrodes of respective ones of theswitching semiconductor elements.

5. A magnetic amplifier controlled power circuit according to claim 1,in which each of the saturable magnetic cores is further wound with agate winding and both ends of each of the gate windings are connectedwith a diode through a capacitor respectively between an outputelectrode and the control electrode of one of the semiconductorswitching elements, and further condenser charging diodes are connectedbetween one end of each of the gate windings and outer end of each ofthe capacitors, respectively.

6. A magnetic amplifier controlled power circuit according to claim 1wherein said semiconductor switch elements are formed by siliconcontrolled rectifiers.

7. A magnetic amplifier controlled power circuit according to claim 6wherein a commutating capacitor is connected between corresponding loadterminals of said silicon controlled rectifiers.

8. A magnetic amplifier controlled power circuit according to claim 7 inwhich said pair of output windings comprise first and second windingportions each portion being wound on and extending over a respective oneof said pair of saturable magnetic cores.

9. A magnetic amplifier controlled power circuit according to claim 8 inwhich each of the saturable magnetic cores is further wound with a gatewinding and both ends of each of the gate windings are connected with adiode through a capacitor respectively between an output electrode andthe control electrode of one of the semiconductor switching elements,and further condenser charging diodes are connected between one end ofeach of the gate windings and the outer end of each of the capacitorsrespectively.

10. A magnetic amplifier controlled power circuit according to claim 9in which each of the saturable magnetic cores is further wound with afeedback winding which is connected in series with the load and the DC.power source so that current flowing in the load also flows through saidfeedback windings.

References Cited UNITED STATES PATENTS 3,034,015 5/1962 Schultz 331-1131X 3,078,380 2/1963 Ingrnan 30788.5 3,189,748 6/1965 McMurray 330-8 X3,209,227 9/1965 Berman et a1. 30788.5 3,237,126 2/1966 Baycura et a1.3311 13 3,251,006 5/1966 Mehwald 331-113 ROY LAKE, Primary Examiner.

